Physical vapor deposition components and methods of formation

ABSTRACT

A PVD component forming method includes inducing a sufficient amount of stress in the component to increase magnetic pass through flux exhibited by the component compared to pass through flux exhibited prior to inducing the stress. The method may further include orienting a majority crystallographic structure of the component at (200) prior to inducing the stress, wherein the induced stress alone is not sufficient to substantially alter surface grain appearance. Orienting structure may include first cold working a component blank to at least about an 80% reduction in cross-sectional area. The cold worked component blank can be heat treated at least at about a minimum recrystallization temperature of the component blank. Inducing stress may include second cold work to a reduction in cross-sectional area between about 5% to about 15% of the heat treated component. At least one of the first and second cold working can be unidirectional.

TECHNICAL FIELD

[0001] The invention relates to physical vapor deposition (PVD)components, for example, sputter targets, and methods of forming PVDcomponents and sputter targets, including magnetic flux enhancementmethods for PVD components.

BACKGROUND OF THE INVENTION

[0002] Sputtering is a common physical vapor deposition (PVD) processused often in semiconductor processing as well as other processing andfabrication. The properties of a PVD component, such as a target, imposevarying effects on properties exhibited by a deposited film. Grain sizeis known to influence deposited film uniformity and is preferably lessthan about 100 microns. Further, as grain size increases, a phenomenonknown as secondary re-crystallization can be observed wherein isolateddomains of extremely large grains (greater than about 200 microns)appear in a component material. Secondary re-crystallization can also bedetrimental to deposited film uniformity. Other properties of acomponent material may effect deposited film uniformity and limit targetlife as well.

[0003] Accordingly, a need exists to reduce grain size of sputteringtargets and identify material properties beneficial to forming depositedfilms and prolonging target life.

SUMMARY OF THE INVENTION

[0004] In one aspect of the invention, a PVD component forming methodincludes inducing a sufficient amount of stress in the component toincrease magnetic pass through flux exhibited by the component comparedto pass through flux exhibited prior to inducing the stress. The methodmay further include orienting a majority crystallographic structure ofthe component at (200) prior to inducing the stress, wherein the inducedstress alone is not sufficient to substantially alter surface grainappearance.

[0005] In another aspect of the invention, a physical vapor deposition(PVD) component forming method includes first cold working a componentblank to at least about an 80% reduction in cross-sectional area. Thecold worked component blank may be heat treated at least at about aminimum recrystallization temperature of the component blank and secondcold worked to a reduction in cross-sectional area between about 5% toabout 15% of the heat treated component. By way of example, at least oneof the first and second cold working can comprise cold rolling. Thecomponent blank can consist essentially of nickel. At least one of thefirst and second cold working can be unidirectional and the heattreating may be performed with a fluidized bed furnace. Also, the heattreating can include substantially uniformly heating the cold workedcomponent blank at least to the minimum recrystallization temperature inless than about 60 minutes. The cold worked component blank can bemaintained at least at the minimum recrystallization temperature forless than about 60 minutes.

[0006] In another aspect of the invention, a sputter component formingmethod can include unidirectionally first cold working a component blankto at least about an 80% reduction in cross-sectional area and heattreating the cold worked component blank at least at about a minimumrecrystallization temperature of the component blank. A sufficientamount of stress may be induced in the heat treated component toincrease magnetic pass through flux exhibited by the heat treatedcomponent compared to pass through flux exhibited prior to inducing thestress.

[0007] In a further aspect of the invention, a sputter target formingmethod can include unidirectionally first cold rolling a target blankconsisting essentially of nickel to at least about an 85% reduction incross-sectional area. Heat treatment of the cold rolled target blank canoccur at a temperature between about 427° C. (800° F.) to about 482° C.(900° F.) for less than about 60 minutes. Second cold rolling of theheat treated target blank can occur to a reduction in cross-sectionalarea of about 10% of the heat treated component. The second cold rolledtarget blank may exhibit at least about 70% of a surface area at leastwithin selected boundaries of a surface of the second cold rolled targetblank having a (200) texture.

[0008] In another aspect of the invention, a magnetic flux enhancementmethod for a sputter component includes combining unidirectional coldworking of a sputter component with heat treatment at about a minimumrecrystallization temperature and orienting predominant crystallographicstructure preferentially at (200). The method may-include additionalunidirectional cold working in a same direction as initially coldworked.

[0009] In a still further aspect of the invention, a PVD componentincludes nickel exhibiting a (200) texture over at least about 50% of asurface area at least within selected boundaries and having a sufficientamount of residual stress to exhibit higher magnetic pass through fluxcompared to pass through flux exhibited absent such stress. Additionalaspects of the invention include PVD components or targets produced bythe methods described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Preferred embodiments of the invention are described below withreference to the following accompanying drawing.

[0011] The FIGURE shows a chart comparing magnetic pass through flux ofa sputter target according to the present invention compared to aconventional target.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The need to reduce grain size of sputter targets and identifycrystallographic orientations and magnetic properties beneficial toforming sputter films has prompted investigation of physical vapordeposition (PVD) component forming methods. Observation indicates thatcrystallographic orientation and magnetic softness or hardness may alsoinfluence sputter film uniformity. Magnetically soft materials mayattenuate the magnetic flux from a sputter apparatus cathode, focusingthe magnetic field to a small portion of a sputter target. The focusedfield can result in a sharp, deep sputter track that acceleratesburn-through and limits target life.

[0013] In the context of the present application, “magnetically soft”materials exhibit a tendency to lose magnetization more quickly incomparison to a “magnetically hard” material. Magnetically softmaterials often can be magnetized and demagnetized readily with littleor no permanent magnetization (remanence). Generally, magnetically hardmaterials are more difficult to magnetize, but retain remanentmagnetization. Also, a “sputter component” used in the context of thepresent application denotes sputter targets as well as other componentsin a sputter chamber that may undergo sputtering. The processingparameters described herein for PVD component forming methods andmagnetic flux enhancement methods pertain particularly to sputtertargets containing nickel, but may also apply to PVD components of othercompositions.

[0014] In one aspect of the invention, a PVD component forming methodincludes first cold working a component blank to at least about an 80%reduction in cross-sectional area. Next, the cold worked component blankmay be heat treated at least at about a minimum recrystallizationtemperature of the component blank. The heat treated component blank canbe second cold worked to a reduction in cross-sectional area betweenabout 5% to about 15% of the heat treated component.

[0015] The high level of first cold work may assist in reducingsecondary recrystallization effects that result in anomalous rapid graingrowth in isolated domains. Typically, the objective of the cold workingis to minimize the artifacts of pre-existing structure, such as grainsize and texture, from the starting component blank. The artifacts canbe merely cosmetic (swirls, ghosts, etc.) but can also be non-uniformstructures in portions of the first cold worked component. It isdesirable to maximize uniformity by cold working and observationindicates that about 80-90% cold work can be adequate. Preferably,cross-sectional area is reduced by at least about 85% to obtain apreferred level of uniformity and minimization of artifacts.

[0016] Cold working preferably comprises cold rolling, however,extrusion, drawing, forging, and other cold working methods known tothose skilled in the art may also be suitable. Also, preferably coldrolling or other cold working can be unidirectional to produce a highlevel of (200) crystallographic orientation. One disadvantage ofunidirectional cold rolling is generation of scrap material.Conventionally, “round to round” rolling allows a higher utilizationlevel for starting material compared to unidirectional rolling, thatgenerates more scrap because of limitations on rolling directions.

[0017] However, unidirectional rolling provides advantageouscrystallographic orientation. For example, the first cold workedcomponent blank may exhibit an orientation ratio of at least 50% (200)or, preferably, at least about 70% (200). In measuring orientationratio, at least 50% or at least 70% of a surface area at least withinselected boundaries of a surface of the first cold worked componentblank may exhibit a (200) texture. Cross-rolling or “round-to-roundrolling” can be detrimental, even in small amounts, to obtaining amajority (200) texture. However, simple unidirectional cold rolling of anickel sputter target blank has been observed to produce a majority(200) texture. Preferably, the component blank consists essentially ofnickel. However, other materials, particularly those having aface-centered cubic crystalline structure, may be suitable to achievethe advantages of the various aspects of the invention. The first coldworking, as well as the second cold working, may occur at a temperatureof about 20° C. (68° F.) or some other suitable temperature known tothose skilled in the art to be considered cold working.

[0018] The heat treating may comprise substantially uniformly heatingthe cold worked component blank at least to the minimumrecrystallization temperature in less than about 60 minutes. Such aheating step, or annealing, is desirable since lengthy, high temperatureannealing is known to lead to secondary recrystallization and producethe detrimental effects of PVD component microstructure described above.The heated, cold worked component blank may be maintained at least atthe minimum recrystallization temperature for less than about 60minutes.

[0019] The initial heating and maintaining the temperature may beperformed in a fluidized bed furnace. Fluidized bed furnaces can impartquick and uniform heat transfer to the cold worked PVD component blank.A variety of fluidized bed furnaces known to those skilled in the artmay be suitable for accomplishing the heat treating described herein. Avariety of heat transfer media may be used in the fluidized bed furnace,for example, alumina has proven suitable. Other fast-transfer methods,such as quartz-bulb (infrared) or electric induction furnace, may beused in the place of a fluidized bed furnace to heat the PVD componentblank quickly and uniformly.

[0020] After maintaining the cold worked component blank at thedescribed temperature, the component blank may be air cooled to 20° C.(68° F.) or another desired temperature. Alternatively, the componentblank may be quenched to a temperature less than the minimumrecrystallization temperature. A suitable heat treating temperature maybe between about 371° C. (700° F.) to about 1200° C. (649° F.) or,preferably, between about 427° C. (800° F.) to about 482° C. (900° F.).The range of 800° F. to 900° F. is particularly suitable for a sputtertarget blank consisting essentially of nickel.

[0021] After heat treating, the PVD component blank preferably exhibitsan average grain size of less than about 50 microns. Average grain sizecan be measured by a variety of techniques, for example, one suitabletechnique is ASTM Test Method E112. When measuring average grain size ortexture, as in a (200) texture, such measurement may occur withinselected boundaries of at least a portion of a surface area of the PVDcomponent blank. As an example, the measured area defined by theselected boundaries may include at least about a statisticallyrepresentative area. The statistically representative area may becalculated by any current or future method known to those skilled in theart. Also, it may be desirable to evaluate whether an outer surface of aspecimen accurately reflects grain size or texture of the overallmicrostructure by removing an outer surface to expose inner portions ofa specimen. An unrepresentative measurement might skew data such that amore narrow or wide distribution of grain size or texture is calculatedthan would result from evaluating the entirety of measurable surfaces ofa specimen. Evaluating all of the surfaces of a specimen that areconducive to the measurements indicated (i.e., measurable) may bepossible. Even so, evaluating representative areas is more efficient andthus desirable. Rules of thumb or other methods may be known in the artfor selecting a representative area, in addition to Test Method E112referenced above.

[0022] Second cold working the heat treated component blank may be usedto reduce cross-sectional area to between about 5% to about 15% of theheat treated component. The small amount of cold working after heattreatment has been observed to create a small amount of residual stressin the target and yield a relatively large increase in the magnetic fluxthat may pass through a PVD component blank as measured perpendicular tothe blank face. The amount of stress is small enough to be virtuallyundetectable visually and mechanically and has not been observed todegrade sputtered films formed from such a component. It appears thatthe induced stress alone is not sufficient to substantially altersurface grain appearance.

[0023] Preferably, the second cold working reduction in cross-sectionalarea is about 10%. Also, preferably the second cold working comprisescold rolling and can comprise a different cold working process than usedfor the first cold working. The second cold working is also preferablyunidirectional as described for the first cold working, but only onemight be unidirectional. Preferably, the first and second cold workingare both unidirectional and each are in the same direction. Working inthe same direction further minimizes any impact of the second coldworking on desirable grain size and texture obtained from first coldworking and heat treating.

[0024] Accordingly, the method of the present aspect of the inventioncan produce a PVD component that exhibits a (200) texture over at leastabout 50% of a surface area. The component may also exhibit an averagegrain size of less than about 50 microns. The grains may have anadequate amount of residual stress to enhance magnetic flux. In thismanner, a PVD component will exhibit a small grain size and also exhibita crystallographic orientation properly stressed to allow a higher passthrough flux (PTF) than absent the stress, prolonging target life. FIG.1 is a chart showing an overall increase in PTF for a (200) nickelsputter target produced according to the present aspect of the inventionin comparison to a conventional (220) nickel sputter target withoutinduced stress.

[0025] One possible explanation for the PTF improvement of the inventionin the case of nickel targets relates to the magnetostriction propertiesof nickel. Speaking simplistically, a magnetic field causes the facecentered cubic crystalline structure of nickel to constrict. When nickelgrains of a sputter target are oriented with a (200) texture, a magneticfield perpendicular to the target face produces constriction in adirection also perpendicular to the target face. A portion of themagnetic field is thus involved in the constriction, affecting PTF.Inducing stress in the target to produce constriction before exposure toa magnetic field is observed to increase PTF. It is presumed that theinduced constriction reduces further constriction by the magnetic field,involving less of the magnetic field and allowing more flux.

[0026] Accordingly, in one aspect of the invention, a PVD componentforming method includes inducing a sufficient amount of stress in thecomponent to increase magnetic pass through flux exhibited by thecomponent compared to pass through flux exhibited prior to inducing thestress. A variety of stress inducing methods other than cold working maybe suitable to accomplish the method. The method may further includeorienting a majority crystallographic structure of the component at(200) prior to inducing the stress, wherein the induced stress alone isnot sufficient to substantially alter surface grain appearance. In thismanner, beneficial characteristics of grain size and texture are largelyunaffected, but PTF can be improved. It is conceivable that texturesother than (200) and materials other than nickel may also be suitablefor practicing the methods described herein with analogous advantages.

[0027] In another aspect of the invention, a sputter component formingmethod may include unidirectionally first cold working a component blankto at least about an 80% reduction in cross-sectional area. The coldworked component blank may be heat treated at least at about a minimumrecrystallization temperature of the component blank. A sufficientamount of stress may be induced in the heat treated component toincrease magnetic pass through flux exhibited by the heat treatedcomponent compared to pass through flux exhibited prior to inducing thestress. Such a method can achieve at least some of the advantagesdescribed herein as desirable for sputter components. Inducing stressmay include unidirectionally second cold working the heat treatedcomponent to a reduction in cross-sectional area between about 5% toabout 15%. of the heat treated component. The second cold working usedin the described method may further improve the desirable properties ofthe sputter component.

[0028] In a further aspect of the invention, a sputter target formingmethod can include unidirectionally first cold rolling a target blankconsisting essentially of nickel to at least about an 85% reduction incross-sectional area. The cold rolled target blank can be heat treatedat a temperature between about 427° C. (800° F.) to about 482° C. (900°F.) for less than about 60 minutes. The heat treated target blank can besecond cold rolled to a reduction in cross-sectional area of about 10%of the heat treated component. At least about 70% of a surface area atleast within selected boundaries of a surface of the second cold rolledtarget blank may exhibit a (200) texture.

[0029] In another aspect of the invention, a magnetic flux enhancementmethod for a sputter component may include combining unidirectional coldworking of a sputter component with heat treatment at least at about aminimum recrystallization temperature. The method may further includeorienting predominant crystallographic structure preferentially at (200)followed by additional unidirectional cold working in a same directionas initially cold worked.

[0030] In keeping with the aspects of the invention described aboveregarding methods of forming PVD components, a PVD component in anotheraspect of the invention may consist essentially of nickel exhibiting a(200) texture over at least about 50% of a surface area at least withinselected boundaries. As described, the selected boundaries may define arepresentative test area. The component may have a sufficient amount ofresidual stress to exhibit higher magnetic pass through flux compared topass through flux exhibited absent such stress.

[0031] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A physical vapor deposition (PVD) component forming method comprisinginducing a sufficient amount of stress in the component to increasemagnetic pass through flux exhibited by the component compared to passthrough flux exhibited prior to inducing the stress.
 2. The method ofclaim 1 wherein the inducing a sufficient amount of stress comprisescold working to a reduction in cross-sectional area between about 5% toabout 15%.
 3. The method of claim 1 further comprising orienting amajority crystallographic structure of the component at (200) prior toinducing the stress, wherein the induced stress alone is not sufficientto substantially alter surface grain appearance.
 4. The method of claim3 wherein the orienting the majority crystallographic structurecomprises cold working a component blank to at least about an 80%reduction in cross-sectional area followed by heat treating at least atabout a minimum recrystallization temperature of the component blank. 5.The method of claim 4 wherein the reduction in cross-sectional area isat least about 85%.
 6. The method of claim 1 wherein the componentexhibits a (200) texture over at least about 50% of a surface area atleast within selected boundaries.
 7. The method of claim 1 wherein thecomponent exhibits an average grain size of less than 50 microns.
 8. Themethod of claim 1 wherein the component consists essentially of amaterial having a face-centered cubic crystalline structure.
 9. Themethod of claim 1 wherein the component consists essentially of nickel.10. A PVD component forming method comprising: first cold working acomponent blank to at least about an 80% reduction in cross-sectionalarea; heat treating the cold worked component blank at least at about aminimum recrystallization temperature of the component blank; and secondcold working the heat treated component blank to a reduction incross-sectional area between about 5% to about 15% of the heat treatedcomponent.
 11. The method of claim 10 wherein the second cold workedcomponent blank exhibits a (200) texture over at least about 50% of asurface area at least within selected boundaries.
 12. The method ofclaim 11 wherein the second cold worked component blank exhibits a (200)texture over at least about 70% of the surface area.
 13. The method ofclaim 10 wherein at least one of the first and second cold workingcomprises cold rolling.
 14. The method of claim 10 wherein the componentblank comprises a sputter target blank.
 15. The method of claim 10wherein the component blank consists essentially of nickel.
 16. Themethod of claim 10 wherein the first and second cold working occur atabout 20° C. (68° F.).
 17. The method of claim 10 wherein at least oneof the first and second cold working is unidirectional.
 18. The methodof claim 10 wherein the first and second cold working are bothunidirectional and each in a same direction.
 19. The method of claim 10wherein the heat treating comprises: substantially uniformly heating thecold worked component blank at least to the minimum recrystallizationtemperature in less than about 60 minutes; and maintaining the coldworked component blank at least at the minimum recrystallizationtemperature for less than about 60 minutes.
 20. The method of claim 10wherein the heat treating is performed with a fluidized bed furnace. 21.The method of claim 10 wherein the heat treating occurs between about371° C. (700° F.) to about 649° C. (1200° F.).
 22. The method of claim21 wherein the heat treating occurs between about 427° C. (800° F.) toabout 482° C. (900° F.).
 23. The method of claim 10 wherein the secondcold working reduction in cross-sectional area is about 10%.
 24. Asputter component forming method comprising: unidirectionally first coldworking a component blank to at least about an 80% reduction incross-sectional area; heat treating the cold worked component blank atleast at about a minimum recrystallization temperature of the componentblank; and inducing a sufficient amount of stress in the heat treatedcomponent to increase magnetic pass through flux exhibited by the heattreated component compared to pass through flux exhibited prior toinducing the stress.
 25. The method of claim 24 wherein inducing thestress comprises unidirectionally second cold working the heat treatedcomponent blank to a reduction in cross-sectional area between about 5%to about 15% of the heat treated component.
 26. A sputter target formingmethod comprising: unidirectionally first cold rolling a target blankconsisting essentially of nickel to at least about an 85% reduction incross-sectional area; heat treating the cold rolled target blank at atemperature between about 427° C. (800° F.) to about 482° C. (900° F.)for less than about 60 minutes; and second cold rolling the heat treatedtarget blank to a reduction in cross-sectional area of about 10% of theheat treated component, at least about 70% of a surface area at leastwithin selected boundaries of a surface of the second cold rolled targetblank exhibiting a (200) texture.
 27. A magnetic flux enhancement methodfor a sputter component comprising combining unidirectional cold workingof a sputter component with heat treatment at least at about a minimumrecrystallization temperature and orienting predominate crystallographicstructure preferentially at (200) followed by additional unidirectionalcold working in a same direction as initially cold worked. claims 28-33.(canceled).